This invention is an improvement on co-pending application Ser. No. 887,495, filed Jul. 16, 1986, entitled "Thermal Sensor", and assigned to the same assignee as the present invention. The teachings of the co-pending application are incorporated herein by reference. In the co-pending application the invention is directed to a pixel size sensor of an array of sensors, for an infrared microbridge construction of high fill factor, made possible by placing the detector microbridge on a second plane above the silicon surface carrying the integrated components and bus lines. The improvement in the present invention is directed to a structure which increases the sensitivity.